Electrical apparatus



Dec. 19, 1961 L. H. SEGALL 3,

ELECTRICAL. APPARATUS Filed Sept. 29. 1955 [Fl [Eu 4 IO\T |5 2e L 25 u[FEED 5 INVENTOR. LOUIS H. SEGALL [FEED [E1 BY flmw/ ATTORNEYS 3,014,151ELECTMCAL AHARATUS Louis H. Segall, Sidney, N.Y., assiguor to The BendixCorporation, a corporation of Delaware Filed Sept. 29, 1%5, Ser. No.537,502 13 Clain (Cl. 313-130) This invention relates to electricalapparatus and more particularly to spark gaps for ignition circuits andthe like.

One of the objects of the present invention is to provide a spark gapdevice of novel and simplified constructlon. 1

Another object of the invention is to provide a novelly constructedspark gap which is highly etficient in the conversion of the energy ofthe source of electrical energy into heat energy in the form of a sparkor arc.

A further object is to provide a novel apparatus for producingelectrical sparks which is so constructed that the spark or are isautomatically propelled a substantial distance into a gaseous or othercombustible charge to be ignited.

Still another object is to provide a novel spark gap structure which isparticularly adapted for use in initiating combustion in the burners ofso-called jet or gas turbine type engines and in the cylinders ofreciprocating engmes.

The above and further objects and novel features of the presentinvention will more fully appear from the following detail descriptionwhen the same is read in connection with the accompanying drawings. t isto be expressly understood, however, that the drawings are for purposesof illustration only and are not intended as a definition of the limitsof the invention.

In the drawings, wherein like reference characters refer to like partsthroughout the several views,

FIG. 1 is a sectional view of one form of spark gap device embodying theinvention;

FIG. 2 is a bottom view of the device of FIG. 1;

FIGS. 3 and 5 are views similar to FIG. 1 showing other forms of sparkgap devices embodying the invention; and,

FIGS. 4 and 6 are bottom views of the devices of FIGS. 3 and 5,respectively.

The several embodiments of the invention illustrated in the drawings, byway of example, are in the form of tip or electrode assemblies adaptedfor use in spark or igniter plugs of the type disclosed in pendingapplication Serial No. 221,435, filed April 17, 1951 (now Patent No.

2,786,158). Structures of this type are particularly adapted for use inthe ignition systems of combustion engines wherein it is advantageous tohave a concentrated hot sparkprojected into the combustible charge.

In the embodiment shown in FIG. 1, a tubular metal shell 10 has aninternal flange 11 at one end which supports the electrode assembly andwhich may also serve as one of the gap electrodes. Shell 10 is usuallygrounded to an engine casing or other structure which serves as aconnection to one terminal of a source of electrical energy. In thespecific form shown, however, a separate plate or washer 12 is seated onflange 11 to serve as the ground electrode. The latter has a relativelysmall diameter central opening 14 and is preferably made of a metal,such as tungsten, which has high resistance to erosion by electricalsparks.

Seated on electrode 12 is a novel center electrode assembly comprisingan insulator 15 and a center electrode 16, 17 which, in the form shown,consists of two metallic members 16 and 17 preferably welded together.Member 16 is threaded into the bore of insulator 15 to hold member 17 infirm engagement with an internal flange at the 3,014,151 Patented Dec.19, 1961 lower end of the insulator. The latter has a small centralopening 18 that is concentric with and preferably the same size asopening 14. If desired, the diameter of opening 14 may be slightlygreater than the diameter of opening 18, but the edge of electrode 12.should preferably not overlap any part of the opening 18. Like electrode12, the center electrode member 17 is preferably made of a metal whichhas high resistance to erosion by electrical sparks. The centerelectrode assembly may be held in shell 10 in any suitable manner, suchas by a ring 19 which may have a press lit in the shell or be otherwisesuitably secured therein. 7

For best results the diameter of hole 14, 18 should be within the rangeof about .005 inch to about .060 inch. A diameter of about .025 inch hasbeen found to be very practical from a manufacturing point of view aswell as from an operational point of view in present day ignitionsystems for aircraft engines. The proper distance between groundelectrode 12 and center electrode 17 along the surface or" opening 18,that is, the width of the spark gap, will depend upon other factors,such as the magnitude of the available voltage and the character of thebridging surface 18. If high voltages are available, the surface withinhole 18 may have good insulating qualities, whereas if only low voltagesare available, such as in some known types of condenser dischargeignition circuits, such surface should be rendered semiconductive in anymanner now well understood in the art, that is, in the art of so-calledshunted-surface spark gaps or" the character shown in theabove-mentioned application Serial No. 221,435. For conventional presentday ignition systems the axial width of the spark gap in the illustrateddevice may vary from about .015 inch to about .090 inch. The axialthickness of ground electrode 12 is determined primarily by its abilityto resist wear under operating conditions, but it should be chosen toavoid the absorption thereby of too great an amount of heat and, hence,energy from the sparks.

The embodiment of FIG. 3 differs from that above described only in thatthe wear resistant ground electrode plate 20 is of reduced diameter andsilver soldered or otherwise suitably secured within the inner peripheryof flange 11 and is provided with a plurality of holes 21 in addition tothe central hole 14. The ceramic piece 15 is also provided withadditional holes 22. in registry with openings 21, thereby forming aplurality of constricted or constrained spark gaps having substantiallythe same characteristics as the single gap of FIG. 1. In this type ofconstruction the sparks will occur in different openings as theelectrodes are worn away, thereby increasing the efficiency and theeffective operating life of the unit.

The embodiment of the invention illustrated in FIG. 5 is likewisesimilar in many respects to the two above de scribed, except that bodyflange 11 serves as the ground electrode, and the communication betweenthe electrodes is through and along the walls of a narrow slit Z5, 26cut transversely across shell 10 and insulator 15. The gap surface isthus increased While providing a restricted or constrained channel orslot in which the spark is more etficiently formed and from which thespark is propelled into the combustion chamber. If desired, more thanone slit or slot 25, 26 may be provided, in which event the same mayintersect at the center axis or extend parallel to one another. Thus,increased sparking surface is provided so that as the metal of theelectrodes is eroded at one sparking path, the sparks will occur along adifferent path, thereby increasing the efiective operating inchto .025inch has been found most practical. As in Q the other embodiments, theWalls of slot 26 in insulator 15, which walls bridge the gap between theelectrodes 11 and 17, may be either semi-conductive or nonconductive,depending upon the type and magnitude of the available voltage.

It will be understood that in each of the embodiments illustrated anddescribed, the center electrode is to be connected by a suitableconductor (not shown) to a source of electrical energy which may be inthe nature of a storage condenser or any other known type of source. Theother electrodes 12, 20 and 11 are generally connected to the otherterminal of the source through socalled ground or if desired, a returnconductor may be provided.

Although only a limited number of embodiments or modifications of theinvention have been. illustrated in the drawings and described in theforegoing specification, it is to be expressly understood that theinvention is not limited thereto. For example, the separate plate typeof ground electrode 12 shown in FIG. 1 may be adapted to the embodimentsof FIGS. 3 and 5, the composite type of electrode 11, 20 of FIG. 3 couldbe adapted to the other embodiments, and the unitary flange type ofelectrode 11 in FIG. 5 could be used in the other two embodiments. Theslit 25 in the ground electrode of FIG. 5 may be slightly wider than thesiit 26 in the ceramic part 15, but there should be no overlap of thelatter by the ground electrode- Various changes may be made in thespecific design and arrangement of the parts illustrated withoutdeparting from the spirit and scope of the invention, as the same willnow be understood by those skilled in the art.

What is claimed is:

1. A spark gap device comprising an insulator having oppositely disposedsurfaces and at least one narrow cylindrical passage connecting saidsurfaces, an electrode engaging one said surface and having asubstantially plane surface extending substantially directly across andbridging one end of said passage, and electrode means engaging the othersaid surface and having a narrow cylindrical passage which is insubstantial registry with and forms a continuation of said first-namednarrow passage in said insulator, the diameter of said narrow passagesbeing within the range of .005 inch to .060 inch.

2. A spark gap device as defined in claim 1 wherein there are aplurality of said narrow passages in the insulator each having one endbridged by said electrode and a corresponding plurality of registeringnarrow passages in said electrode means.

3. A spark gap device as defined in claim 1 wherein the gap between saidelectrode and said electrode means along the wall of the passage in saidinsulator is within the range of .015 inch to .090 inch. 7

4. A spark gap device as defined in claim 1 wherein said narrow passageshave diameters of the order of .025 inch.

5. A spark gap device comprising. an insulator having oppositelydisposed surfaces and at least one narrow passage in the form of anelongated transversely extending slot connecting said surfaces, anelectrode engaging one said surface and having a surface extendingdirectly across and bridging one end of said passage, and electrodemeans engaging the other said surface and having a narrow passage whichis in substantial registry with and forms a continuation of saidfirst-named narrow passage in said insulator.

6. A spark gap device as defined in claim 5 wherein said slot has awidth Within the range of .010 inch to .060 inch.

7. A spark gap device as defined in claim 1 wherein the surface portionof said insulator within said firstnamed passage is semi-conductive.

8. Ina spark gap device, two electrodes spaced in spark gap relation toeach other, and an insulator interposed between said electrodes andbridging the gap therebetween, said insulator having at least one narrowcylindrical passage therein within which sparks between the electrodesare constrained to occur, one of said electrodes having a substantiallyplane surface extending substantially directly across and closing saidpassage at one end thereof and the other of said electrodes having atleast one cylindrical passage constituting an extension of the internalsurface of said first-named passage, the diameter of said passages beingof the order of about .025 inch.

9. A spark gap device as defined in claim 8 comprising a tubular shellin which said insulator is supported, said shell having an internalflange at one end thereof which constitutes at least a support for saidother electrode. I

10. A spark gap device as defined in claim 9 wherein one of saidelectrodes is interposed between said insulator and said internal flangeon said shell.

11. A spark gap device as defined in claim 9 wherein one of saidelectrodes is secured to the inner periphery of said flange.

12. In a spark gap device, a tubular metallic shell having an internalflange, a first metallic electrode and an insulator supported by saidflange in the shell, and a second metallic electrode insulated from saidshell and spaced from said first electrode by said insulator, said firstelectrode and insulator having narrow cylindrical openings therein insubstantial registry to provide a constricted passage closed at one endby a substantially plane surface of said second electrode and throughwhich arcing may occur between said electrodes, the diameter of saidpassage being less than .060 inch.

13. A spark gap device as defined in claim 12 wherein said narrowopenings have diameters of the order of about .025 inch.

14. In a spark gap device, a tubular metallic shell. having an internalflange, a first metallic electrode and an insulator supported by saidflange in the shell, and a second metallic electrode insulated from saidshell and spaced from said first electrode by said insulator, said firstelectrode and insulator having narrow openings therein in the form ofelongated transversely extending slots and in substantial registry toprovide a constricted passage closed at one end by said second electrodeand through which arcing may occur between said electrodes.

15. A spark gap device comprising two spaced electrodes, and aninsulator bridging the gap between said electrodes, the active surfacesof said electrodes and the bridging surface of said insulator forming acylindrical recess in which the sparks between the electrodes areconstrained to occur, the closed end of said recess being formed by oneof said electrodes and the diameter of said recess being within therange of .005 inch to .060 inch.

16. In a spark gap device, a tubular metallic shell having an internalflange, an insulator supported by said flange in the shell, and ametallic electrode mounted in said insulator, said insulator and flangehaving narrow cylindrical openings therethrough in substantial registryto provide at least one constricted passage covered at one end by asubstantially flat end surface of said electrode and through whicharcing may occur between said flange and electrode, the diameter of saidconstricted passage being within the range of .005 inch to .060 inch.

17. A spark gap device comprising an insulator having oppositelydisposed surfaces and at least one narrow passage in the form of anelongated transversely extending slot connecting said surfaces, anelectrode engaging one said surface and havinga substantially planesurface extending substantially directly across and bridging one end ofsaid passage, and electrode means engaging the other said surface andhaving a narrow passage which is in substantial registry with and formsa continuation of said first-named narrow passage in said insulator, the

transverse width of said narrow passages being within the range of .005inch to .060 inch.

18. In a spark gap device, a tubular metallic shell having an internalflange, a first metallic electrode and an insulator supported by saidflange in the shell, and a second metallic electrode insulated from saidshell and spaced from said first electrode by said insulator, said firstelectrode and insulator having narrow openings therein in the form ofelongated transversely extending slots in substantial registry toprovide a constricted passage closed at one end by a substantially planesurface of said second electrode and through which arcing may occurbetween said electrodes.

References Cited in the file of this patent UNITED STATES PATENTS SBakke May 26, 1925 Hibbs Jan. 3, 1933 Moore Mar. 7, 1933 Mitchel Sept.15, 1936 Peters Oct. 28, 1941 'Linlor Oct. 24, 1944 Litton Feb. 8, 1947Mitchell Aug. 15, 1950 Smits Oct. 23, 1951 Mascuch Oct. 30, 1951 SmitsMay 15, 1956 Tognola May 22, 1956 Tognola Mar. 19, 1957 Lentz Apr. 22,1958 Watters June 24, 1958 Summerer Feb. 17, 1959 FOREIGN PATENTS GreatBiitain July 21, 1954

